Anti-fouling apparatus



March 14, 1967 s. GALLER 3,309,167

ANTI-FOULING APPARATUS Filed May 21, 1963 2 Sheets-Sheet 1 IELE'LL :3(CASTOR 0| I.)

f|3 ENERGY SYSTEM ENERGY SYSTEM ENERGY SYSTEM x I l .3 C. 35 I C 34INVENTOR SID N EY G A L L E R ATTORNEY March 14-, 1967 Filed May 21,1963 S. GALLER ANTI-FOULING APPARATUS 2 Sheets-Sheet 2 FF: 6 n mnmmmmg62 z 60 E: 000mm}? E1125: so

ENERGY soURoE CLOC K WATER TRANSDUCER TRANSDUCER PROGRAMMER TEMPERATURETEMPERATURE HEATTNG sENsDR SENSOR ELEMENT INVENTOR WATER VELOCITY SIDNEYGALLER DETECTOR ATTORNEY United States Patent 3,309,167 ANTI-FOULIN GAPPARATUS Sidney Galler, 6242 Woodcrest Ave., Baltimore, Md. 21209 FiledMay 21, 1963, Ser. No. 282,184 1 Claim. (CI. 21-61) The inventiondescribed herein may be manufactured and used by or for the Governmentof the United States of America for governmental purposes without thepayment of any royalties thereon or therefor.

The present invention relates to an apparatus to prevent fouling ofmarine equipment by marine biological organisms in the sea. Moreparticularly the invention is directed to apparatus for combatingbarnacles and the like, which tend to attach to and/or deposit heavyencrustations of calcareous-like materials on underwater equipment.

Barnacles have a long and inglorious history in the marine industries.Their razor-sharp shells coat pilings and pier walls, forming a hazardto deck hands and dock hands and dock workers. The same is true ofanchor chains, anchors, nets and other gear, which are submerged fordays and weeks at a time. Most important, the hulls, screws, and ruddersof ships eventually become too burdened and distorted to perform theirfunction and must be cleaned.

The problem has become more serious in modern times. A host of newprecision instruments have been developed for the science ofoceanography to measure sound velocity, depth, temperature, salinity,and similar properties in the sea. Other instruments have been developedfor navigation and purposes of national defense. Not only must many ofthese instruments be built to survive long immersions in the sea, buttheir surfaces must remain reasonably clean to permit them to functionproperly.

It has become the practice in the art to paint or coat such objects, asare mentioned by way of example above, in order to prevent fouling. Someof these coatings have proved successful in preventing this conditionfor short periods, while Others merely slow the process. Such coatingsare often dislodged by accident, leaving the equipment with noprotection. An early attempt to solve the problems involved releasingoil through holes in a ships keel. This method has obviousdisadvantages.

An object of the present invention is, therefore, to provide apparatusto prevent fouling of underwater equipment which involves heatingexternal surfaces exposed to marine organisms.

These and other objectsor attendant advantages of the present inventionwill be best understood with reference to the following specification,taken in conjunction with the accompanying drawings wherein:

FIG. 1 shows the side view of a submarine partly cut away withantifouling structure incorporated in its sonar dome;

FIG. 2 shows the cut away side view of a low frequency sound transducerincorporating antifouling structure;

FIG. 3 shows a hydrofoil craft partly cut away with antifoulingstructure associated with its hydrofoils;

FIG. 4 shows a heating element for use in the structures of FIGS. 1-3using a liquid heat carrier;

FIG. 5 shows a first electrical type of heating element for use in thestructures of FIGS. 1-3;

FIG. 6 shows a second electrical type of heating element for use in thestructures of FIGS. 1-3;

FIG. 7 shows a block diagram of the heating element and energy system ofFIGS. 13; and FIG. 8 shows a cut away view of one embodiment of thevelocity detector in FIG. 7.

- animals involved in the fouling.

In order to appreciate the present invention, it is necessary to know alittle about the life cycle of barnacles. A great deal of research hasbeen done on these organisms and reported in various publications. Oneexample is the publication edited by Dixy Lee Ray entitled, MarineBoring and Fouling Organisms, published in 1959 by the University ofWashington Press, Seattle, Wash.

The development of a" barnacle proceeds in several stages beginning withan ovum or egg. After hatching from the egg the resulting organismproceeds through a series of naupliar stages, in which it exists as afree moving planktonic life form. This generally takes between seven andthirteen days. At least two additional stages are of interest, thecyprid stage and the sessile stage.

When the barnacle reaches the cyprid stage it tends to settle out of itsexclusively liquid environment onto solid objects. The barnacle mayremain in this stage from one to fourteen days, but if it remains morethan three days its development generally ceases at this stage.

If the barnacle successfully settles out and metamorphoses to thesessile or attached stage, the problems associated with this organismbegin. The organism begins to deposit its characteristic calcium shellmaterial. Killing the organism will arrest, but not eliminate thisdeposition. Further, it has been noted that new barnacles settle morereadily on surfaces that are already occupied by others of their breed.In the sessile stage a barnacle is very adaptable and may survive foryears.

It can be seen from the discussion above that at any particular timeunderwater equipment should be protected from organisms in the cypridstage. Earlier stages are no problem. Organisms in the sessile stage aremore diificult to kill and have done irreversible damage.

It has been discovered that heat can be used to prevent the attachmentof the cyprid stage. In geographic loca tions where settlement rates arenormally high, a blockage often occurs during a series of unusually warmdays. Tests have shown that even the most adaptable species in the morefavorable sessile stage cannot endure a temperature over 45 C. about F.for more than a minute without damaging the organism.

While barnacles are perhaps the best known of the fouling organisms itis not always the most important. There are more than 2000 species ofboth plants and In certain instances, a two day accumulation of algae onthe pontoons of an air plane has been sufficient to prevent the aircraftfrom reaching take-off speed. The settlement of all of these organismscan be discouraged by the periodic application of a suificiently hightemperature, e.g. 150 F., at the surface under attack. In contrast,protective coatings are usually designed to discourage only specificspecies of organisms.

FIG. 1 shows a structure in which the above temperature characteristiccan be used to protect underwater sound equipment. submarine 10 with asound transducer 11 mounted on the outer surface of the submarine. Toprevent turbulence, a dome 12 is placed over the transducer and a soundcoupling medium 13 such as castor oil added to fill the space betweenthe transducer and the dome. Heating elements 14 are placed in the dometo quickly elevate the temperature. Energy is supplied to the heatingelements from an energy system 13 Within the submarine.

Other ways of producing the desired heating might be to place theheating elements in the castor oil or to heat the oil in the submarineand circulate it between the dome and the transducer. However, owing tothe efiicient heat sink presented by the sea, it is preferred to applythe heat rapidly as near the external surface as The equipment iscarried aboard a possible. The settlement of organisms on the externalsurface provides a degree of insulation, so that the system is actuallymore efiicient in its working environment. The structure of the heatingelements per se will be discussed presently.

FIG. 2 shows another form which the present invention may take. Thestructure shown is an underwater sound transducer of the type currentlyused in low frequency sonar systems. It is sufficient for presentpurposes to state that this transducer consists of a hollow cubicalhousing 20 with an internal motor 21 which engages the internal surfacesof housing walls only over a small percentage of four nonradiatingwalls. The radiation characteristics of this transducer depends in parton the mass of the housing and its resistance to reciprocal motion inthe water. A more complete description of one form of this transducermay be found in patent application Ser. No. 611,798, filed Sept. 24,1956 by John Chervenak, now abandoned.

The accumulation of barnacles on this type of transducer presents aserious problem. The extra mass causes a shift in the center frequencyof their operating characteristic. Roughening of the surfaces lowers theefficiency of the device and alters the directivity pattern. Such anaccumulation may be prevented by means of a heating element 22 attachedto inner surfaces of the walls, which again are made and operated in amanner to be described presently.

The heating element is connected to an external energy system which maybe the same system supplying the motor element 21. The two elements caneasily operate on a time sharing basis, since the timing of the formeris not critical. To prevent barnacle accumulations, heating elements 34and 35 are placed in all parts of the hydrofoil which are submerged whenthe craft is at rest. The heating elements are connected to an energysource Within the boat and operated in a manner to be describedpresently.

FIG. 4 shows one form the heating elements may take. In this case heatis carried by a heat transfer liquid flowing through tubing 40 embeddedin the wall 41 or other member to be heated. The tubing is preferablymade from a material having good heat conducting properties such ascopper or aluminum, although other materials may be used. If used in thestructure of FIG. 1, the tubing and heat transfer liquid should have thesame composition or sound propagation characteristics as the dome andcastor oil.

FIG. 5 shows a second form of heating element which may be employed withstructures having walls of electrical insulating materials. A length ofwire 50 consisting of electrically conducting material is imbedded inthe wall 51. 'By passing an electric current through the wire ohmicheating is induced which is transferred to the wall. In thermoplasticmaterials the temperature of the wire must remain below the softeningpoint of the material. The use of ribbon shaped conductors will improveheat transfer in such instances.

FIG. 6 shows an electrical heating element primarily suitable for metalstructures. A radiant heating conductor 69 is mounted in close spacedrelationship to the metal wall 61 by means of refractory ceramicinsulators 62. The conductor is a conventional tungsten alloy whichmaintains its strength at red heat. If desired, a polished metalreflector (not shown) may be mounted parallel to the wall with heatingelement between and spaced from the two former elements. The surface ofthe wall may also be roughened and darkened to improve its heatabsorbing qualities.

FIG. 7 shows an energy system such as shown in FIGS. l-3 in blockdiagram form. While this system can conceivably consist merely of amanually controlled energy source 60, a few simple refinements make thedevice much easier to use. For example, a temperature sensor attached tothe transducer can be used to control the output of the energy source tomaintain a constant temperature at the heated surface, thereby savingfuel. Also, a clock programmer can be used to automatically energize thesystem at appropriate intervals.

Two additional devices can also be employed to conserve fuel and heaterlife. A water temperature sensor may be connected to the programmer todisable it when the seawater temperature is too high for settlement andmetamorphoses of cyprids. Also a water velocity detector may be employedto disable the clock programmer when a water current is passing over theprotected surface and organisms are unable to settle on it.

The actual structure of various elements shown diagrammatically in FIG.7 is not a critical feature of the invention. The temperature sensorsmay be the same type of thermostat and aquastat used in home heatingsystems or ovens. The clock programmer may be the same type as found incompletely automatic home ovens. The energy source for the heatingelements of FIGS. 5 and 6 will be a battery or generator and the variouscontrol elements will open or close high current relays to the heatingelement. A system using the heating elements of FIG. 4 may be similarwith electrically controlled valves instead of high current relays,similar to the valves found in automatic clothes washers anddishwashers. The FIG. 4 system obviously can use oil or gas burners asan energy source.

FIG. 8 shows a convenient form of water velocity detector for use withthe present invention. Briefly, the detector employs a mercury switchattached to the end of a length of flexible cable 81. The cable andswitch are composed of materials having suflicient density to provide anegative buoyancy in seawater. With the upper end of the cable attachedto the structure containing the heating elements, clock programmer,etc., the unit hangs vertically in the sea as shown. Attachmentgenerally will involve a conventional watertight seal through anon-radiating wall.

The switch consists of a housing 86, at least the inner surface 82 ofwhich is formed of conducting material, and a drop of conductingmaterial such as mercury. The housing is a solid of revolution havingits axis normally vertical. The bottom of the housing is slightlyconcave to gravitationally center the drop in the vertical position. Twoconductors 84 and 85 enter the housing from the cable. First conductor84 is electrically connected to the inner surface of the housing, andthe other, 85, extends along the vertical axis of the housing to theupper surface of the conductive drop 83. When displaced by a watercurrent the attitude of the housing shifts, as does the drop, therebyopening the circuit which energizes the programmer.

The ideal method of operating the device will vary according to itsgeographical location and the season of the year. Biological data may becompiled in suitable book form for use by a human operator. However,data so far available indicates that an automatic system operating a fewminutes every other day might provide sufficient protection. For greatersafety, operating periods of half an hour each day are relatively easyto supply.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It would be impossible todisclose fully all of the marine equipment such as seaplanes, buoys,mines, nets, etc., in which the present apparatus may be installed. Itis therefore to be understood that within the scope of the appendedclaim the invention may be practiced otherwise than as specificallydescribed.

What is claimed is:

An apparatus for preventing the settlement of organisms in sea wateronto the exposed surface of the walls of submerged objects, comprising:

a heating element mounted internally of said sub- 5 merged object inheat transfer relationship to said walls,

an electrical source for energizing said heating element coupledthereto,

a water temperature sensing means operative to control said electricalsource in response to temperature changes in the sea water, and

deactivating means external to said object for disabling said electricalsource through activation of said deactivating means in response to theflow of sea Water relative to said walls of said object and saiddeactivation means.

References Cited by the Examiner UNITED STATES PATENTS 58,742 10/'1-86 6Weems l14222 6 632,919 9/ 18-99 Farley l44222 660,646 10/ 1900 'Mason144-222 900,929 1-0/1908 Howe 144222 X 1,319,550 10/1'919 Wilson 114-222FOREIGN PATENTS 890,265 2/ 1962 Great Britain.

I. ZATARGA, Assistant Examiner.

